Easy open can end with preformed pouring aperture



g- 29, 1967 w. G. REYNOLDS ETAL 3,338,462

EASY OPEN CAN END WI TH PREFORMED POURING APERTURE Filed March 11, 1965 INVENTORS M4 mmr Z 5 r/vo40s BY 7%u ,2 ATTORNEYS United States Patent 3,338,462 EASY OPEN CAN END WITH PREFORMED POURING APERTURE William G. Reynolds and Robert S. Davidson, Richmond, Va., assignors to Reynolds Metals Company, Richmond, Va., a corporation of Virginia Filed Mar. 11, 1965, Ser. No. 438,915 2 Claims. (Cl. 22053) ABSTRACT OF THE DISCLOSURE Opening means for an apertured can end comprising a peel'able pull tab peripherally sealed about the aperture and having a molded-in-situ plastic plug filling the aperture which material is tightly bonded to the tab but is free of tight adhesion to the underside of the can end adjacent the aperture to facilitate withdrawal of the plug with the pull tab.

This invention relates to an easy-open can end construction, and more particularly to a novel and simple can end construction wherein a peelable pull tab sealingly overlies a pre-apertured metallic can end externally thereof and means are provided for preventing contact between the container contents and the exposed raw edge of the pouring aperture.

Hitherto easy-open can ends for containers subject to high internal pressures have been of two general types, both being relatively diflicult and expensive to fabricate in comparison with the present invention. One well known form utilizes an imperforate can end suitably scored to define a rupturable tear strip as in the patent to Walsh 2,978,140. Such imperforate end constructions have received greater attention in commercial development heretofore inasmuch as the use of a scored but totally imperforate end has been believed to be the simplest means of preventing leakage under internal gaseous pressure on the order 100 p.s.i. or greater, as may occur with carbonated beverage contents or during sterilizing of sealed and filled containers in a retort.

It has been recognized, however, that a metallic can end having a pre-cut pouring or dispensing aperture possesses a number of desirable attributes, including the elimination of scoring steps during manufacture, and the prevention of upturned and rough or relatively sharp edges which result from the upward and outward forces on the can during removal of a scored tear strip, which edges may be objectionable or injurious to the consumer, etc. Some effort has thus been directed to easy-open can ends having pre-cut pouring apertures, as for example in the patent to Houghtelling 2,870,935. While such constructions are often satisfactory with relatively pressureless can contents, difficulty has been experienced in maintaining a leakproof seal at the precut aperture against high internal gaseous pressures normally encountered in carbonated beverage cans, especially during heat processing thereof.

A more complete discussion of the problems involved in the manufacture of beverage cans having sealed precut pouring apertures is to be found in the co-pending application of Reynolds et a1. Ser. No. 395,165, filed Sept. 9, 1964. The easy-open pre-cut can end construction of the present invention embodies certain principles disclosed in the said co-pending application in achieving the novel and useful construction set forth herein.

It has been found that with certain liquid contents, including various beverages of the soft-drink type, the exposed raw metal present around the pouring aperture can attack the coloring matter of the beverage or otherwise adversely affect the same, thereby contaminating and ice.

adulterating the contents and rendering the same commercially unacceptable.

It is therefore a principal object of our invention to provide an easy-open beverage can having a pre-cut pouring aperture wherein any contamination of the beverage contents by exposed metal around the pouring aperture is positively prevented.

It is a further object of our invention to provide I a protected raw edge around a pre-cut can end aperture in an easy-open container embodying the novel principles set forth in our said copending application.

It is an additional important object of our invention to provide an easy-access container of the type contemplated wherein raw edge protection is achieved simultaneously with the securing of the peel tab to the can end, thereby eliminating the need for additionalprocess: ing or handling steps in the manufacture thereof.

It is a further object to provide a molded-in-situ protective plug for the exposed aperture edge thereby eliminating any necessity for expensive pre-shaped seal means.

Other objects and advantages will be apparent from the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a perspective view of a representative can incorporating the easy-access closure of the present invention, the pouring aperture being illustrated in dotted mes;

FIGURE 2 is a fragmentary sectional viewof the container taken on the line 2-2 of FIGURE 1;

FIGURE 3 is an enlarged fragmentary sectional view of the can end closure taken on the line 33 of FIG- URE 1;

FIGURE 4 is an enlarged fragmentary sectional view of the tab and a back-up anvil associated therewith prior to final securing of the tab to the closure.

Referring to the drawings, I have shown at 10 an exemplary container as for canned beverages or the like which includes a cylindrical body side wall 11, a lower end closure of any well known type at 12, and a metallic top closure at 13 which is double seamed or otherwise secured to the upper end of the body 11.

The upper end closure 13 is provided with a precut pouring aperture 14 which in the illustrated embodiment is of somewhat egg-like or elliptical configuration along a radius of the circular can end 13 as seen in FIGURE 1. A pull tab T is bonded to the closure 13 solely externally thereof to sealingly overlie'the dispensing aperture 14, the tab T including an unbonded portion 16 which may be readily grasped with the fingers and lifted to manually peel the tab from the can end.

Referring in more detail to the enlarged views of FIG- vURES 3 and 4, it will be seen that in the disclosed embodiment the can end 13 includes the metal central panel thereof at 15 of aluminum or the like provided with a conventional heat-resistant protective liner 17 on the undersurface thereof to prevent the metal closure 15 from contaminating the container contents, and an external coating at 18 which cooperates with the tab underside coating 22 as will be described hereinafter.

Similarly, the pull tab T of the illustrated embodiment comprises a relatively rigid strip of aluminum 19 which is externally coated with a protective finish coating at 20 comparable to that at 17 on the can end. The tab is further provided with an undersurface coating at 22 to which is adhered a relatively thick strip of plastic 21. Strip 21 is a thermoplastic resin and is employed principally to seal and protect the raw metal edge 23 surrounding aperture 14 from deleterious contact with the can contents.

The confronting coatings 18 and 22 provide the mechanical bond between the tab T and end closure 13. As

set forth more fully in our copending application, the composite adhesive system at 18 and 22 is uniquely capable of forming a bond which is capable of resisting the aforesaid high-internal pressure stresses acting in tension against the underside of tab T, while being yieldable to peeling forces in order to readily remove the tab to dispense the can contents. More particularly, and to further facilitate under standing of the heat seal system with which the novel raw-edge protecting strip 21 is associated, the coatings 18 and 22 each individually comprise an epoxy primer applied to the respective substrates and 19, and an overlying vinyl resinous coating in respective contact with opposite surfaces of strip 21.

One example of an epoxy primer which has been found successful in actual use is marketed by Interchemical Corporation under the designation B-11l3, and a suitable resinous coating for use therewith in making up the composite coatings 18 and 22 is marketed by Stoner-Mudge Company, known as S-988005.

In heat sealing the tab T to the end 13 there is a molecular interaction between the composite coatings 18 and 22, whereby the tab 15 is firmly bonded to the end 13 and will not yield or rupture therefrom under tension stresses to cause leakage even when subjected to internal gaseous pressure on the order of 100 p.s.i. as is commonly encountered in carbonated beverage cans, especially during sterilizing of the filled containers in heat retorts, for example.

While the described adhesive system has been found to be a unique and highly practical means of securing a peelable tab to a pre-apertured can end to thereby gain the foresaid advantages of easy dispensing of the can contents without injury to the consumer and avoiding scoring steps during manufacture, it will be seen that the metallic can end 15 is fully internally coated at 17 except for the annular area 23 bounding the aperture 14, at which locale the exposed raw metal of closure 15 would, if unprotected, be exposed to the can contents. In the instance of certain soft drink type beverages, the provision of a metallic end closure as at 15 of aluminum or steel has been found to attack the beverage contents, causing contamination of the same. Thus while the easy-open closure and adhesive system of our copending application may be readily employed with and is highly advantageous for use with any number of liquid or granular container contents, there exists the specific problem in connection with the particular soft drink or other specific liquid contents which may be adversely affected by the exposed metal 23 of the can end surrounding the pouring aperture 14.

This problem is solved in a unique and effective manner by the instant invention and wherein not only is the raw edge 23 protected by a molded-in-situ coating but the protection thereof is effected and achieved simultaneously with the heat-securing of the tab T to the can end 13 whereby no additional handling or fabricating steps are required in the manufacture thereof.

More particularly, and as seen in FIGURE 4, the pull tab T overlies and is tightly bonded to the plastic strip 21, which in turn rests upon the can end bounding the aperture 14. Strip 21 is of sufficient thickness, somewhat exaggerated in the drawings, so as to provide suflicient coating material to protect the edge 23. An acceptable thickness for strip 21 which has been found to be satisfactory in practice is on the order of 3 mils.

In securing tab T to the can end, as well as to simultaneously protectively coat raw edge 23, an anvil element 24 is placed in underlying contact with the underside of the can end 15, the anvil being recessed as shown at 25 to define a recess beneath the can end 13 extending outwardly from the periphery of aperture 14. In the preferred embodiment, the anvil is provided with an annular groove 26 at the periphery of recess 25 to insure smooth flow of the plastic from strip 21thereinto under heat and pressure and flow upwardly into contacting,

lightly sealed relation with the internal liner 17 of the can end.

Accordingly, upon the application of heat and pressure to the tab T disposed in the FIGURE 4 position, the plastic strip 21 of thermoplastic resin will be softened and squeeze downwardly through the aperture 14 and into the recess 25 of the anvil 24, flowing into the groove 26 therearound to fully cover and protect the exposed raw edge 23 of the aperture 14, while simultaneously the desired bond will be formed between the unique coatings 18, 22 and strip 21, whereby upon the completion of the heat sealing operation and removal of the anvil 23, the can end with the tab sealed thereto will partake of the configuration illustrated in FIGURE 3.

In this connection it is important to note that the portions of the tab 21 underlying the aperture edge as formed by recess 25 do not contribute in significant material respects to the proper securing of the tab T to the can end 13, but rather serve principally to insure that the exposed raw edge 23 of the aperture 14 is fully sealed against any possibility of contact with container contents which could be contaminated by contact therewith. The tight leakproof and pressure-resistant bonding of the tab T to the can end 13 is effected solely by the interaction of the adhesive system 18 and 22 and the thin strip portion 21 therebetween. In the view of FIGURE 3, the illustrated parts are considerably enlarged, and it will be appreciated that in the actual working dimensions of usual container structures the portion of the tab 21 between coatings 18 and 22 will be of virtually microscopic thinness, whereby the effective bond is achieved by interaction and fusing of the portions 18 and 22.

It is apparent that the particular configuration of the tab T and the pouring aperture 14 may vary from the preferred form shown herein without departing from the inventive concept herein disclosed. Similarly, the tab may be other than an aluminum sheet, as for example, a strip of relatively rigid polystyrene with a foil gas barrier of the character set forth in our copending application. Similarly, it will be appreciated that the can body 11 may be aluminum, steel, tin plate, or other like constructions known in the art, while the connection between the can end and the body may be a simple clinch seam, double seam or other construction conventional in the art. It follows, then, that the present invention with its attendant advantages may be usefully employed with any container known in the art wherein the tab adhesive system permits the container to be employed with relatively highpressure gaseous contents on the order of p.s.i. and wherein such contents as may be adversely affected by contact with the exposed metallic raw edge of the pouring aperture are safeguarded by the instant novel molded-in-situ covering thereover.

What is claimed is:

1. An easy-open metal can end construction for a filled container, said end including a panel having a preformed pouring aperture therein,

a relatively rigid pull tab disposed in external overlying relation to said aperture and to the portion of said panel surrounding said aperture,

resinous adhesive heat seal means bonding said tab to said surrounding panel portion, said adhesive means having the characteristics of being resistant to tension stresses whereby leakage through said aperture is prevented when said tab is subjected to internal gaseous pressures, but is yieldable to peeling forces to permit peel-removal of said tab,

and a molded-in-situ plug of plastic material fully filling said aperture to cover and protect the edge thereof from contact with the container contents, said plug being molded to form simultaneously with heat-sealing of said tab to said end, and wherein said plastic material is tightly bonded to the underside of said tab and underlies said panel in surrounding relation to said aperture edge while being free from tight 5 6 adhesion thereto, whereby removal of said pull tab aperture and having portions thereof disposed in withdraws said plastic material from said aperture underlying engagement with said can end around said and aperture edge. raw edge, with said plug being tightly bonded to said 2. In an easy-open metal can end construction for a tab while free from tightly bonded relation to said hermetically sealed container subject to internal pressure 5 can end adjacent said aperture edge. substantially in excess of atmospheric pressure wherein said end includes a preformed pouring aperture there- References Cited through and a pull tab adhesively bonded to said can end UN STATES P N zglcellgpirfielrrrally thereof in overlying sealing relation to 2,870,935 1/1959v Houghteuing 22O 53 10 3,251,515 5/1966 Henchert et a1. 220-43 the improvement comprising means for preventing the raw metal annular edge of said pouring aperture THERON CONDON, Primary Examiner. from contacting the contents of said container, said means including a molded-in-situ plug filling said HALLASssmm Examine"- 

1. AN EASY-OPEN METAL CAN END CONSTRUCTION FOR A FILLED CONTAINER, SAID END INCLUDING A PANEL HAVING A PREFORMED POURING APERTURE THEREIN, A RELATIVELY RIGID PULL TAB DISPOSED IN EXTERNAL OVERLYING RELATION TO SAID APERTURE AND TO THE PORTION OF SAID PANEL SURROUNDING SAID APERTURE, RESINOUS ADHESIVE HEAT SEAL MEANS BONDING SAID TAB TO SAID SURROUNDING PANEL PORTION, SAID ADHESIVE MEANS HAVING THE CHARACTERISTICS OF BEING RESISTANT TO TENSION STRESSES WHEREBY LEAKAGE THROUGH SAID APERTURE IS PREVENTED WHEN SAID TAB IS SUBJECTED TO INTERNAL GASEOUS PRESSURES, BUT IS YIELDABLE TO PEELING FORCES TO PERMIT PEEL-REMOVAL OF SAID TAB, 